Metal forming presses generally include die sets or platens which have helical compression die springs associated therewith. The die springs are used to guide and align the die sets during repeated pressing operations and to facilitate easy die opening after the press forming. In most die forming apparatus, means are provided for vertically affixing the die springs to the die sets, generally in die spring pockets.
Frequently, the die springs break or lose compressive strength after repeated pressing operations and it becomes necessary to replace them. Obviously, it is desirable to accomplish such replacement as quickly and simply as possible. Typically, die springs are secured in cylindrical die spring pockets in the die sets by means of some kind of retainer. U.S. Pat. No. 4,521,005 discloses one such type of retainer having a generally circular base which includes a plurality of axially extending tangs circumferentially disposed around the periphery of the base. Each tang includes a retaining wall and gripping barb which engage the first coil of the spring, firmly securing it to the circular base. The spring and attached mount are then inserted into the die spring pocket where the barbs engage the cylindrical pocket walls. However, these retainers are difficult to fabricate quickly and precisely and require that the tangs be specifically aligned to engage both the die spring and the die spring pocket wall. The tangs are easily misaligned during production, resulting in an uneconomical waste of time and energy in physically straightening the tangs.
Yet another type of die spring retainer is known in the trade as a Danly Spring Retainer and consists of a housing into which the die spring is secured. The spring and housing combination must then be secured into an appropriately configured cylindrical die spring pocket. Danly Spring Retainers are spring-size specific, and their use requires mathematical computations based on factors such as the spring pressure at initial compression, die travel, and die spring diameter to select an appropriate size spring.
The foregoing die spring retainers represent some of the prior art approaches to the problem of vertically affixing die springs to die sets. Despite the various designs of spring retainer, such prior art retainers are less than satisfactory owing to their fabrication complexity and to the required inserts for precise springs selection computations attendant upon their use.
It will then be appreciated that there is yet a need for die spring retainers of relatively simply design which may be employed to vertically affix die springs of various sizes to die sets. It is further desired that such retainers be secured to die sets by utilizing pre-existing pilot screws found in the die sets, and that they be easily and inexpensively fabricated. The present invention addresses the inadequacies of the prior art by providing a simple, inexpensive die spring retainer which may be secured to a die set by means of a pre-existing pilot screw. These and other advantages of the present invention will be readily apparent from the drawings, discussions and claims which follow.